A receiving device, such as an integrated circuit (IC), typically includes an alternating current (AC) coupling circuit through which an input differential data signal is received. The AC coupling circuit typically includes a pair of capacitors having respective input terminals configured to receive the input differential signal. The AC coupling circuit further includes a pair of resistors coupled in series between respective output terminals of the capacitors. An output differential signal is generated at the output terminals of the capacitors.
If the input differential signal has balanced (e.g., random) data with substantially equal number of logic ones (1s) and zeros (0s), then the output differential signal is logically (data wise) substantially the same as the input differential signal, with the exception that the AC coupling circuit, being configured as a high pass filter (HPF), removes the DC component of the input differential signal.
However, if the input differential data signal has one or more time intervals with unbalanced data (e.g., a relatively long series of logic ones (1s) or zeros (0s)), the input differential signal functions similar to a direct current (DC) signal during such one or more time intervals. As a result, the capacitors begin to charge due to the temporary DC signal. The charged capacitors produces voltage drops across them. This results in a decay of the differential amplitude of the output differential signal.
When the input differential data signal becomes balanced again, the charged capacitors induce an offset in the output differential signal. This is termed in the art as baseline wander. Accordingly, the disclosure relates to techniques for correcting or reducing baseline wander of an output differential signal for an AC coupling circuit.